Managing the Software Life
Cycle of PHP Applications
Stefan Priebsch, thePHP.cc
PHP Quebec, Montreal

Stefan Priebsch
Co-Founder and Principal Consultant

Software Lifecycle

Software Lifecycle
ve
si
Inception
●
ur
Elaboration
●
c
Re
Construction
●
Transition
tly
●
Production
● en
Retirement
●
er
h
In

„The
perfect project plan
is possible if one first documents a list of
all the unknowns.“
unknowns.“
-- Bill Langley

Process Models

Waterfall Model
Systems Engineering
●
Analysis
●
Design
●
Coding
●
Testing
●
Deployment and maintenance
●

Waterfall Model
Systems Engineering
●
Analysis
●
Design
●
Coding
●
Testing
●
Deployment and maintenance
●

„The most important single aspect of
software development is to be clear
about what you are trying to build.“
-- Bjarne Stroustrup

„Life can only be
understood backwards,
backwards,
but it must be
lived forwards.“
forwards.“
-- Soren Kierkegaard

Other Models
V-Model
●
Spiral Model
●
Rational Unified Process
●
Extreme Programming
●
Scrum
●
Test-driven Development
●
...
●

Linear Processes Fail

Iterative Processes Win

Excerpts from
„Rational UML Document Set,
Semantics, Chapter 5.2“:

„The name of a Type instance is
a Name instance representing
the name of the Type;
its value may not be a null name [...]“
„The name of an Instance instance is
optional, but where it exists it must not
be a null name [...]“
„An Instance instance with no name is
always considered to have a unique
name, distinct from any other Instance
instance with no name.“

„There's no sense being
exact about something
if you don't even know
what you're talking about.“
-- John von Neumann

Heavy Processes Fail

Lightweight Wins

Agile Methods
Individuals and interactions
●
over processes and tools
Working software
●
over comprehensive documentation
Customer collaboration
●
over contract negotiation
Responding to change
●
over following a plan

Agile Development
Working software is delivered
●
frequently
Working software is the principal
●
measure of progress
Even late changes in requirements
●
are welcomed
Regular adaptation to changing
●
circumstances

Small Incremental Steps

„Complexity kills.“
„It sucks the life out of developers,
it makes products difficult to plan,
build and test, it introduces
security challenges
and it causes end-user and
frustration.“
frustration.“
administrator
-- Ray Ozzie

„Complexity kills.“
„It sucks the life out of developers,
it makes products difficult to plan,
build and test, it introduces
security challenges
and it causes end-user and
frustration.“
frustration.“
administrator
-- Ray Ozzie

Reuse
Stick to standards
●
Open source = open knowledge
●
Reuse Experience
●
Use Components
●
Use Frameworks?
●

Basic Quality Assurance
Static Code Analysis
●
Lint (php -l)
●
PHP_CodeSniffer
●
Software Metrics
●
PHPUnit
●
PHP_Depend
●
Output validation
●
Tidy
●
HTML/CSS validation
●

PHP_CodeSniffer
FILE: /path/to/code/myfile.php
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
FOUND 5 ERROR(S) AFFECTING 5 LINE(S)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
2 | ERROR | Missing file doc comment
20 | ERROR | PHP keywords must be lowercase; expected \"false\" but found \"FALSE\"
47 | ERROR | Line not indented correctly; expected 4 spaces but found 1
51 | ERROR | Missing function doc comment
88 | ERROR | Line not indented correctly; expected 9 spaces but found 6
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
FILE: /path/to/code/yourfile.php
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
FOUND 1 ERROR(S) AND 1 WARNING(S) AFFECTING 1 LINE(S)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
21 | ERROR | PHP keywords must be lowercase; expected \"false\" but found
| | \"FALSE\"
21 | WARNING | Equals sign not aligned with surrounding assignments
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­

„Measuring programming progress by
lines of code is like measuring
aircraft building progress
by weight.“
weight.“
-- Bill Gates

Testing
Unit Tests
●
Integration Tests
●
System Tests
●
Acceptance Tests
●
Testing Tools:
●
PHPUnit (http://www.phpunit.de)
●
Selenium (http://seleniumhq.org/)
●

„A fault discovered and
corrected in the unit testing phase is
more than a hundred times
cheaper than if it is done after delivery
to the customer.“
-- Barry Boehm

Deployment
svn checkout
●
Compressed archive (tar.gz, zip, bzip2)
●
PEAR installer
●
New in PHP 5.3: phar archives
●
rsync
●

Deployment
Always automate deployment
●
Use 3 Systems
●
Development
●
Integration/Staging
●
Live
●
Consider virtual machines
●

Continuous Integration
Automate builds
●
Integrate frequently
●
Run automated tests
●
Tools:
●
CruiseControl
●
(http://cruisecontrol.sourceforge.net)
phpUnderControl
●
(http://phpundercontrol.org)

Continuous Integration

Debugging
Create a test to expose each bug
●
Keep the test, and run it often
●
Tool: xdebug (http://www.xdebug.org)
●
Tracing
●
Remote Debugging
●

„Debugging is twice as hard
as writing the code in the first place.“
„Therefore, if you write the code
as cleverly as possible,
possible,
you are, by definition,
not smart enough
to debug it.“
-- Brian W. Kernighan

Maintenance

„The cost of adding a feature isn't
time it takes to code it.“
it.“
just the
„The cost also includes the
obstacle to
addition of an
future expansion.“
expansion.“
-- John Carmack

„Large-program structure must
created but must
not only be
also be maintained if decay is
to be avoided or postponed“
-- Meir Lehman

Refactoring
Improve the design of software without
●
changing its behaviour
„Clean up“ code
●
Not adding new features
●
Keep refactoring your code constantly
●
Use unit tests to ensure you don't
●
break anything

„You know you've achieved
perfection
in design, not when you have
nothing more to add,
but when you have
nothing more to take away.“
away.“
-- Antoine de Saint-Exupery

Scaling
Do not guess where to start
●
Profile your code
●
how often are functions called
●
how long does execution take
●
! that's just one execution path
●
Tool: xdebug (http://www.xdebug.org)
●

„Premature optimization
is the root of all evil.“
-- Donald Knuth

Scaling in a Nutshell
Reduce I/O
●
Disks are slow
●
Network is slow
●
Caching
●
Bytecode caching
●
Data caching
●
Result caching
●

Migration
Code E_STRICT-compatible
●
in PHP 5.3: watch out for E_DEPRECATED
●
Compare trace logs between versions
●
Refactor when fixing issues
●

Today's Take-Aways

Today's Take-Aways
Keep things simple
●
Accept change
●
Test early and often
●
Automate tests and deployment
●

not at all important
„It's
to get it right the first time.“
time.“
„It's vitally important
to get it right the last time.“
time.“
-- Andrew Hunt and David Thomas

http://www.thephp.cc
Twitter: thephpcc
stefan@thephp.cc
http://www.priebsch.de
Twitter: spriebsch
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